Cellular v.s. SRDs & Machine to Machine Communications

Cellular v.s. SRDs & Machine to Machine Communications

For many years the Cellular Companies have been looking at M2M as a lucrative stream of income. However, with press reports of thinning rural coverage, the introduction of new services such as 4G and 5G and the news that 2G and then 3G will be shortly terminated should we think hard before committing to using cellular for M2M data gathering or remote monitoring and go back to using SRSs as we did in the 80’s?

So let us take a deep look into the pros and cons of cellular vs SRDs for M2M and telemetry.

SRDs networks can be as simple as a single transmitter and receiver or as complex as a network of many linked nodes spanning many square km. The big distinction with SRDs is that there are no rules on protocols, no licence fees and no SIM contracts to worry about. SRD devices tend to be power efficient and nodes with battery lives reaching decades are readily available. On the downside you do need to establish and fund your own networks and there is no guarantee against interference.

Cellular based M2M requires each and every device to have a SIM card and contract. Connectivity with the exception of 2G where you can use the “GSM dial” for pier to pier communications, data communication is from the field device to a central location, typically as SMS gateway or GPRS port. The issue and growing concern with the cellular networks is security. It was recently reported by the Institute of Directors (IOD) in London, that as many as 50,000 cyber attacks were reported in the UK alone last year. Many of these attacks have been targeted at “big business” including ISPs and mobile operators. We suspect these attacks could be behind some of the regional blackouts in GPRS and internet traffic that we have seen over the last 2 years.

The next major issue is battery life. GSM/GPRS devices consume approximately 100 fold the energy of a SRD to send a small packet message, with most energy consumed in making the initial connection to the network. This makes long term battery operation more challenging and if the network is busy even more energy is wasted whilst waiting to connect, making overall battery life difficult to predict.

Then there is the cellular network coverage and dynamics. Coverage in rural areas is already thin and the ability to steer masts to alter coverage patterns is great for crowds of people at a soccer match but can cause havoc with a M2M applications.

Finally, there is the big question over obsolescence, with reports already talking of the demise of 2G by 2015 and 3G by 2021, we lost analogue in the 90’s and progress will dictate the life of 2G and 3G is finite.

Ultimately we have to leave you to make the decisions – however, all we can say is that LPRA members have seen marked return in customers who have been disappointed with the performance of cellular M2M.

As a closing note simply ask your network provider for a SLA and see what response you get! At least with SRDs you have some control over your destiny.

Brian M. Back  Managing Director Radio Data Networks Limited / LPRA Council Member